JP6506787B2 - Deposition method - Google Patents

Description

  The present disclosure relates to a film forming method, and more particularly to a film forming method, a film forming apparatus, and a medical material for forming a diamond-like carbon film on the inner wall surface of a long capillary.

  An artificial blood vessel is a medical material that has been in increasing demand in recent years. A commonly used artificial blood vessel is made of expanded-polytetrafluoroethylene (PTFE) which has been expanded and made porous. Although ePTFE is a highly biocompatible material, it is not sufficient in terms of occlusive properties. For this reason, the use of an ePTFE vascular prosthesis less than 6 mm in diameter is very risky.

  Although thin artificial blood vessels using materials derived from humans and animals exist, there are problems in terms of safety and stable supply. For this reason, a thin artificial blood vessel which is not of biological origin and which is not easily occluded is required.

Diamond-like carbon (DLC) films, which are amorphous carbon films containing sp ² carbon, sp ³ carbon and hydrogen, are excellent in biocompatibility. Therefore, by forming the DLC film on the inner wall surface of the artificial blood vessel, it is expected that the occlusion of the artificial blood vessel can be less likely to occur. However, it is not easy to form a DLC film on the inner wall surface of a long tubule such as an artificial blood vessel.

  As a method of forming a DLC film on the inner wall surface of the tube, there is, for example, a method of inserting a discharge electrode inside the tube (see, for example, Patent Document 1). Also, instead of inserting an electrode into the interior of a tubular body, a method of forming a film inside the tubular body to form a film by sandwiching the tubular body between two electrode plates has also been studied (for example, Patent See literature 2).

JP, 2015-147974, A JP 2008-192567 A

  However, the conventional film forming method has the following problems. In the case of inserting the discharge electrode into the inside of the tube, a discharge electrode longer than the tube to be film-formed and thinner than the inner diameter of the tube is required. The discharge electrode to which high pressure is applied needs a certain thickness or more, and it is practically impossible to form a film on the inner wall surface of a thin tube of 6 mm or less. In addition, when the distance between the discharge electrode and the inner wall surface is reduced, the metal component detached from the discharge electrode may be attached to the inner wall surface. If the discharge electrode is a carbon electrode, metal deposition does not occur, but it is difficult to form a thin and long carbon electrode.

  When a tube is sandwiched between two electrodes, a large electrode plate is required to form a film over the entire long tube. There is also a method of moving the tube between the electrodes or moving the electrodes along the tube, but in this case a mechanism for moving is required. In addition, since it is necessary to contain hydrocarbon gas inside the tubular body, in the case of a porous artificial blood vessel, even if it is disposed directly between electrodes, a film can not be formed successfully.

  It is expected that forming a DLC film on the inner wall surface is also useful in catheters and the like because the biocompatibility and the effect of reducing the friction on the inner surface can be obtained. However, the same problems as in the case of artificial blood vessels also occur in the medical material for long tubules used for catheters and the like.

  An object of the present disclosure is to enable a DLC film to be easily formed on the inner wall surface of a long narrow tube medical material.

  In one aspect of the film forming method of the present disclosure, a non-conductive long capillary is disposed in a chamber capable of adjusting the internal pressure, and a raw material gas containing a hydrocarbon is supplied to the inside of the long capillary. A step of generating plasma to form a diamond-like carbon film on the inner wall surface of the long tubule, in which the discharge electrode is disposed at one end of the long tubule and the other end is open An alternating current bias is intermittently applied between the discharge electrode and a counter electrode provided apart from the long thin tube in the chamber.

In one aspect of the film forming method, the long tubule can be porous and housed in an outer cylinder whose inner diameter is larger than the outer diameter of the long tubule and disposed in the chamber.

  In this case, the long tubule can be an artificial blood vessel.

  In one aspect of the deposition method, the long tubule can be a catheter.

  In one aspect of the film formation method, the counter electrode can be an inner wall surface of the chamber.

  One aspect of a film forming apparatus of the present disclosure includes a chamber capable of adjusting an internal pressure, a gas supply unit for supplying a hydrocarbon gas into the chamber, a discharge electrode and a counter electrode provided in the chamber, and a discharge electrode. A power supply unit for intermittently applying an alternating voltage between the electrode and the counter electrode, the discharge electrode being attached to one end of the nonconductive long tubule, and the counter electrode being separated from the long tubule By discharging, plasma is generated in the long tubule, and a diamond-like carbon film is formed on the inner wall surface of the long tubule.

  The one aspect | mode of the film-forming apparatus is further equipped with the outer cylinder which accommodates a long tubule, and the long tubule can be made porous.

  One aspect of the medical material of the present disclosure is a non-conductive long tubule having an inner diameter of 0.1 mm or more and 6 mm or less, a length of 2 cm or more, and a diamond-like carbon film formed on the inner wall surface. Have.

  In one aspect of the medical grade material, the long tubule can be an artificial blood vessel or a catheter.

  According to the film forming method of the present disclosure, the DLC film can be easily formed on the inner wall surface of the long narrow tube medical material.

It is a schematic diagram which shows the film-forming apparatus which concerns on one Embodiment. It is sectional drawing which shows the connection part of a discharge electrode. It is sectional drawing which shows the modification of the connection part of a discharge electrode. It is sectional drawing which shows the modification of a discharge electrode. It is sectional drawing which shows the modification using an outer cylinder. It is sectional drawing which shows the modification of a counter electrode. It is a Raman spectrum of a sample.

  FIG. 1 shows a film forming apparatus used in the present embodiment. The film forming apparatus has a chamber 101 that accommodates the long capillary 102 to be film-formed. A vacuum exhaust unit 110 and a gas supply unit 115 for supplying a gas for film formation into the chamber 101 are connected to the chamber 110, and the internal pressure can be adjusted. In addition, a power supply unit 120 that supplies power is connected, and plasma can be generated in the chamber 101.

  In the present embodiment, the vacuum evacuation unit 110 has a vacuum pump 112 and a valve 113. In the present embodiment, the gas supply unit 115 includes a cylinder 116 and a mass flow controller 117. The gas supply unit 115 can also supply a plurality of gases. In the present embodiment, the power supply unit 120 includes a voltage generator 121 and an amplifier 122, and applies an AC voltage between the discharge electrode 125 and the counter electrode. The counter electrode is a ground electrode and is an inner wall of the chamber 101.

  One end of the elongated capillary 102 disposed in the chamber 101 is disposed at the position of the discharge electrode 125, and the other end is in an open state. After the pressure in the chamber is reduced, a raw material gas containing hydrocarbon is supplied from the gas supply unit 115, and an alternating voltage is applied between the discharge electrode 125 and the inner wall of the chamber 101 which is a counter electrode. The application of the alternating voltage raises the temperature around the discharge electrode 125. As a result, the pressure in the elongated capillary 102 becomes slightly lower than that outside the elongated capillary 102, and a hydrocarbon plasma is generated in the vicinity of the discharge electrode 125. Since the other end of the long tubule 102 is released, the generated plasma travels in the long tubule 102 toward the release end, and plasma is generated throughout the long tubule 102. As a result, a DLC film is formed on the inner wall surface of the elongated capillary 102.

From the viewpoint of sufficiently purging the chamber 101 in the raw material gas, it is preferable to reduce the pressure to temporarily 1 × 10 ^-3 Pa~5 × 10 ^-3 approximately Pa in the chamber before deposition. As the hydrocarbon contained in the raw material gas, methane, ethane, propane, butane, ethylene, acetylene, benzene and the like used in a conventional CVD method can be used, and methane is preferable from the viewpoint of handling. Further, as the source gas, an organic silicon compound such as tetramethylsilane or an oxygen-containing organic silicon compound such as hexamethyldisiloxane can be vaporized and used. The source gas can be diluted with an inert gas such as argon, neon and helium as necessary, and is preferably diluted with argon from the viewpoint of handling. When diluting, the ratio of hydrocarbon to inert gas is preferably about 10: 1 to 10: 5.

  From the viewpoint of uniformly forming the DLC film in the long thin tube 102, the pressure in the chamber 101 is preferably set to about 5 Pa to 200 Pa in a state where the source gas is supplied. Further, the flow rate of the source gas can be about 50 sccm to 200 sccm.

  The bias voltage applied to the discharge electrode 125 at the time of film formation can be about 1 kV to 20 kV. From the viewpoint of avoiding damage to the discharge electrode and temperature rise, the voltage is preferably 10 kV or less. The frequency of the AC voltage is preferably about 1 kHz to 50 kHz. The alternating voltage is preferably a pulse bias applied intermittently from the viewpoint of suppressing the temperature rise. When making an alternating current into a burst wave, it is preferable to make pulse repetition frequency into about 3 pps-50 pps. The tube temperature can be set to 200 ° C. or less by setting the pulse repetition frequency to about 30 pps or less, although it depends on the inner diameter of the long capillary 102, the film formation time, the AC applied voltage, and the like. In order to increase the deposition rate, the pulse repetition frequency may be increased, and in order to suppress the temperature rise, the pulse repetition frequency may be decreased.

  In order to stabilize the discharge and obtain the adhesion of the DLC film, it is preferable to apply an offset negative voltage to the discharge electrode 125. The offset voltage can be about 0 to 3 kV.

The material of the long tubule 102 may be any non-conductive material. In the present disclosure, non-conductive means that the specific resistance is about 1 × 10 ⁸ Ω / cm or more. Specifically, fluorine resin such as PTFE, vinyl chloride resin, polyurethane resin, polyethylene resin, polyolefin resin, silicone resin and the like can be used. Although the specific use of the long tubule is not particularly limited, medical materials used for medical devices in contact with blood such as catheters and artificial blood vessels may be mentioned.

  The inner diameter of the long tubule 102 is not particularly limited, but in the case of an artificial blood vessel or a catheter, it is preferably 10 mm or less, more preferably 6 mm or less, still more preferably 4 mm or less, preferably 0.1 mm or more, more preferably 0. It is 2 mm or more. The length of the long tubule 102 is also not particularly limited, but in the case of an artificial blood vessel or a catheter, it is preferably 2 cm or more, more preferably 4 cm or more, and still more preferably 10 cm or more. From the viewpoint of uniformly forming a film, it is preferably 5 m or less, more preferably 3 m or less, and still more preferably 1.5 m or less. However, it is also possible to form a film on the inner wall of a thin tube of 5 m or more by adjusting the film forming conditions.

  The discharge electrode 125 may be disposed at one end of the long tubule 102. In the present embodiment, the state in which the discharge electrode 125 is disposed at the end of the elongated capillary 102 may be any of the following states. First, as shown in FIG. 2, at least the tip of the discharge electrode 125 can be positioned inside the long thin tube 102. Further, as shown in FIG. 3, the electrode connector 103 is connected to the end of the elongated capillary 102, and at least the tip of the discharge electrode 125 can be positioned inside the electrode connector 103. The electrode connector 103 can be formed of an insulating tube or the like. In FIG. 3, although the electrode connector 103 is a tube externally fitted to the elongated capillary 102, the electrode connector 103 may be a tube internally fitted to the elongated capillary 102. Also, the electrode connector 103 can be formed by combining a plurality of tubes. In this case, if a hard material is used for the connection portion with the long tubule 102 and a flexible material is used for the other portion, handling becomes easy.

The discharge electrode 125 can have an outer diameter smaller than the inner diameter of the elongated capillary 102 or the electrode connector 103 so that the source gas can be supplied into the elongated capillary 102 from the end on the discharge electrode 125 side. . Further, as shown in FIG. 4, the discharge electrode 125 may be hollow so that the source gas may be supplied into the long thin tube 102.

  The discharge electrode 125 may be made of any conductive material, for example, metal. In the case of metal, stainless steel is preferable from the viewpoint of corrosion resistance and the like. If a metal electrode is inserted so as to penetrate the capillary, there is a risk that metal migration from the electrode to the capillary may occur. However, in the case of the film forming apparatus of the present embodiment, when the electrode connector 103 is used, the influence of metal hardly occurs. Even in the case where the electrode connector 103 is not used, the influence of metal hardly occurs at a position separated by about 5 cm or more from the discharge electrode 125. From the viewpoint of avoiding the influence of the metal, it is preferable to use the discharge electrode 125 as a carbon electrode. In the case of the film forming apparatus of the present embodiment, the carbon electrode can also be easily formed.

  If the long tubule 102 is porous and no pressure difference occurs between the inside and the outside of the long tubule 102, plasma can not be generated in the long tubule 102 as it is. In this case, as shown in FIG. 5, film formation can be performed by housing the long thin tube 102 in the outer cylinder 104 so that a pressure difference occurs between the inside and the outside of the outer cylinder 104. .

  The outer cylinder 104 is nonconductive as the long tubule 102 in order to generate plasma inside. Specifically, plastic etc. The outer cylinder 104 can be formed of a flexible soft material or a hard material. By making transparent or translucent, it is possible to obtain the advantage that the generation of plasma can be visually confirmed.

The outer cylinder 104 is made of one having no pores or the like on the wall surface so that a pressure difference is generated between the inside and the outside due to the temperature rise when an AC voltage is applied to the discharge electrode 125. The inner diameter of the outer cylinder 104 may be larger than the outer diameter of the long tubule 102, and the length may be equal to or larger than the length that can accommodate the entire long tubule 102. The opposite end of the outer cylinder 104 is in an open state.

The inner diameter of the outer tube 104 substantially coincide with the outer diameter of the long tubule 102, by the state almost no gap between the outer wall surface and the inner wall surface of the outer cylinder 104 of the long tubule 102, substantially the length Plasma is present only inside the long tubule 102, and film formation can be performed only on the inner wall surface. By enlarging the gap between the outer wall surface of the long tubule 102 and the inner wall surface of the outer cylinder 104, the plasma also exists outside the long tubule 102, and not only the inner wall surface of the long tubule 102 but also the outer wall surface. It is also possible to form a film.

  Although FIG. 5 shows an example in which the discharge electrode 125 is disposed at the end of the elongated capillary 102 by using the electrode connector 103 internally fitted to the outer cylinder 104, the electrode connector 103 is externally fitted to the outer cylinder 104. It can also be done. Further, the tip of the discharge electrode 125 may be positioned inside the outer cylinder 104 without using the electrode connector 103. In this case, the tip of the discharge electrode 125 may be located inside the long tubule 102.

  Even when the long tubule 102 is a catheter or the like and is not porous, the long tubule 102 can be housed in the outer cylinder 104 to form a film.

  In the present embodiment, the counter electrode is the inner wall of the chamber 101. However, as shown in FIG. 6, the counter electrode 126 may be disposed to face the discharge electrode 125 with the elongated capillary 102 interposed therebetween. By arranging the counter electrode 126 in this manner, stable plasma can be generated even when the AC voltage is lowered. Not limited to this, the counter electrode 126 may be provided at any position in the chamber. Even when the counter electrode 126 is in contact with the long tubule 102, plasma can be generated. However, in the case of the counter electrode 126 made of metal, metal contamination of the long tubule 102 can be made less likely to occur by providing the long tubule 102 separately.

  The film thickness of the DLC film formed on the inner wall of the long tubule 102 is not particularly limited, but from the viewpoint of improving the occlusion of the artificial blood vessel and from the viewpoint of reducing the friction coefficient of the inner surface of the catheter Preferably it is 10 nm or more. Further, from the viewpoint of preventing peeling and the like, it is preferably 50 nm or less, more preferably 30 nm or less.

  The film forming time may be such that the required film thickness can be obtained, and an optimum value may be selected according to the film forming conditions such as the inner diameter of the long capillary, AC voltage, pulse repetition frequency, etc. Preferably it is 60 minutes or less from a viewpoint of, More preferably, it is 30 minutes or less, More preferably, it is 10 minutes or less.

<Deposition apparatus>
A DLC film was formed on the inner wall surface of the sample by the film forming apparatus shown in FIG. The chamber 101 was a stainless steel container having a diameter of 200 mm and a length of 500 mm. A vacuum exhaust unit 110 and a gas supply unit 115 are connected to the chamber 101, and the power supply unit 120 is constituted by a voltage generator 121 (SG-4104 manufactured by IWATSUU) and an amplifier 122 (HVA 4321 manufactured by NF Corporation). The discharge electrode 125 was a stainless steel electrode having a diameter of 6 mm and a length of 70 mm. The gas supply unit 115 is configured to supply the source gas from the cylinder 116 of methane gas via the mass flow controller 117. The pressure in the chamber 110 was adjusted by controlling the opening of the valve and the gas supply amount.

<Evaluation of DLC film>
The film formation was confirmed by a Raman spectrometer (RAMAN 11 manufactured by nano photon). Measurement conditions were a light source wavelength of 532 nm, an objective lens of 50 times, a numerical aperture of 0.8, and a diffraction grating of 600 gr / mm.

<Deposition on silicon tube>
A DLC film was formed on the inner wall of nine types of silicon tubes having an inner diameter of 2 mm, 3 mm and 4 mm and lengths of 500 mm, 1000 mm and 1500 mm. The source gas was CH ₄ , the flow rate was 96.2 ccm (room temperature), and the pressure in the chamber was 39.06 Pa. The bias voltage at the time of film formation was 5 kV, and the frequency was 10 kHz. The alternating voltage was applied intermittently for 5 minutes so that the pulse repetition frequency was 10 pps or 30 pps. At the time of film formation, an offset of 2 kV was applied by an amplifier.

  In any of the samples, plasma was generated in the tube from the electrode side to the open end side, and a DLC film was formed on the inner wall surface of the tube.

  When forming a film, a thermo label (manufactured by Wahl) was placed 5 cm from the electrode, and the temperature in the tube was measured. When the pulse repetition frequency is 10 pps, it is 132 ° C. to 154 ° C., 30 pps In the case of, it was 171 ° C-193 ° C.

Deposition on artificial blood vessels
Inside an outer tube made of silicon tube with an inner diameter of 5 mm and a length of 150 mm, put an ePTFE artificial blood vessel (GORE-TEX, SGTW-0415BT) with an inner diameter of 4 mm and an outer diameter of 5 mm and a length of 150 mm. The film was formed. The deposition conditions were the same as in the case of the silicon tube. The film forming time was 5 minutes, 20 minutes and 40 minutes.

Plasma was generated in the artificial blood vessel and a DLC film was formed. FIG. 7 shows an example of measurement of a Raman spectrum. According deposition time increases, weakened specific peak in PTFE, the peak of G-band of the carbon in the vicinity of the peak and 1550 cm ^-1 of the D band of the carbon in the vicinity of 1330 cm ^-1 have emerged.

  100 mm from the open end side of the sample was divided into 20 mm portions, and the adhesion of the film was evaluated for each test piece. Each of the test pieces was in the shape of a dumbbell having a width of 3 mm and a length of 10 mm in the parallel portion and a width of 10 mm in the grip portion. For each measurement piece, a tensile test (force gauge MX-500N, manufactured by IMADA) is performed so that the strain rate becomes 20%, 40%, 60, 80%, 80%, and the film at each strain rate The presence or absence of peeling was confirmed. For each test piece, peeling of the DLC film was not observed even when the tensile test was performed to a strain rate of 80%.

  The film forming method of the present disclosure can easily form a DLC film on the inner wall surface of a long capillary, and is useful as a method of manufacturing a medical material or the like.

101 chamber 102 long capillary tube 103 electrode connector 104 outer cylinder 110 gas supply unit 120 power supply unit 121 voltage generator 122 amplifier 125 discharge electrode 126 counter electrode

Claims (7)

A non-conductive elongated capillary is disposed in a chamber capable of adjusting the internal pressure, and in a state where a raw material gas containing hydrocarbon is supplied, plasma is generated inside the elongated capillary, thereby producing the elongated capillary Forming a diamond-like carbon film on the inner wall surface of the
The long tubule is disposed in the chamber with the discharge electrode disposed at one end and the other end opened.
An alternating current bias is intermittently applied between the discharge electrode and a counter electrode provided apart from the long thin tube.   The film forming method according to claim 1, wherein the long thin tube is porous and is accommodated in an outer cylinder having an inner diameter larger than the outer diameter of the long thin tube and disposed in the chamber.   The film forming method according to claim 2, wherein the long tubule is an artificial blood vessel.   The film forming method according to claim 1, wherein the long thin tube is a catheter.   The film forming method according to any one of claims 1 to 4, wherein the counter electrode is an inner wall surface of the chamber. Chamber with adjustable internal pressure,
A gas supply unit for supplying a hydrocarbon gas into the chamber;
A discharge electrode and a counter electrode provided in the chamber;
A power supply unit for intermittently applying an alternating voltage between the discharge electrode and the counter electrode;
The discharge electrode is attached to one end of the nonconductive elongated capillary, and the opposing electrode is discharged in a state of being separated from the elongated capillary, thereby generating plasma in the elongated capillary, The film-forming apparatus which forms a diamond like carbon film in the inner wall face of the said long thin tube. It further comprises an outer cylinder for accommodating the long tubule,
The film forming apparatus according to claim 6, wherein the long narrow tube is porous.